In general, a conventional laser oscillation device mainly uses cells having uniform thicknesses. In order to realize wavelength-variable lasing, the conventional laser oscillation device is fabricated by injecting a cholesteric liquid crystal with a pitch into the cells having the uniform thickensses. And in order to change pitch, ultraviolet (UV) light or temperature control could be applied.
However, the cholesteric liquid crystal used in the conventional laser oscillation device operates as a laser resonator, and the cells having the uniform thicknesses correspond to Fabry-Perot laser cavity in which a length of the laser resonator is uniformly fixed. Therefore, if lasing is performed by using the conventional laser oscillation device, a laser shows a laser line oscillation in a wide wavelength region but results in inconsecutive wavelength-variable lasing, i.e., an inconsecutive laser wavelength oscillation. Also, an optical parametric oscillator (OPO) which is a conventional consecutive wavelength-variable laser system uses a high-priced optical device. Therefore, cost increases, and a small device is not provided.